This invention relates to an indicator and, more particularly, to a liquid level indicator for storage tanks to indicate when the liquid in the storage tank has substantially reached the rim or top portion of the storage tank when filling the storage tank with the liquid, and also to indicate when the liquid is at or near a low level in the storage tank so that the storage tank can be refilled with the liquid.
The use of liquid level indicators is well known in the art, where such indicators can be used in storage tanks, such as fuel oil storage tanks, in domestic, commercial and industrial fields. These indicators alert the person filling the storage tank at the time when the storage tank is filled, thereby preventing the liquid from spilling on the basement floor, on sidewalks and on streets and, accordingly, thus avoid foul odors, hazardous fumes, accidents, fires and the like which can be caused by the spilled liquid. Furthermore, these indicators alert the owner or person in charge of the storage tank when the liquid in the storage tank is at or near a low level so that the storage tank can be refilled without an interruption in the drawing of the liquid from the storage tank. Accordingly, these indicators reduce human errors and compensate for the inexperience of the person filling the storage tank.
U.S. Pat. No. 1,838,135 discloses a high low gravity tank alarm float to indicate both a high level and a low level of the liquid in the tank, where a float moves up and down on a rod to contact either an upper stop or a lower stop secured to the rod Accordingly, when the float contacts either of the stops on the rod, the float moves the contacted stop which thus moves the rod either upwardly or downwardly to activate an operating bar which is connected to an electrical switch arrangement to give a signal when the level of the liquid in the tank is above or below the predetermined levels.
U.S. Pat. No. 3,646,293 discloses an electrical signal generator and a liquid level indicator associated therewith to indicate different levels of the liquid in a tank. A float is mounted on a tube for up and down movement thereof, where magnets are carried within the float to activate stationary switches which are mounted at predetermined levels within the tube in order to produce pulses to indicate the different levels of the liquid in the tank, where the switches are connected to an electrical system to indicate the particular position of the float at each time a particular switch is activated.